I have 2 Trane XR12 Heat Pumps (a 3 Ton and a 2 Ton) each controlled by Honeywell RTH8500D 'Vision' digital programmable thermostats. I have the thermostats Locked In 24x7 at 69 degrees downstairs and 70 degrees upstairs. (I have no programed features active at the moment until I get this all sorted out and know HPs don't like to keep moving temps up and down)

We just moved in December and got a high elec. bill after 22 days. I decided to watch the meter and noticed that we were using a lot of electricity and noticed that the "AUX HEAT" was running a lot more than I thought it should.

I came home yesterday around 2pm. The outside temp was 60 degrees. I have my thermostats set at 69. When I went upstairs, the first floor unit was not running. Both ambient and setpoint temps were at 69. When I came down, ambient temp was 69, setpoint temp was 69, and the "AUX HEAT ON" indicator was on and the unit was running (of course).

I know that the AUX HEAT should not be kicking on and I'm sure it was not defrosting. I called the HVAC installers and had them take a look at it. They, of course, blamed the thermostats (since I requested to have them put in - they had the old ugly manual ones originally) and then the builder. "Digital thermostats never work right!", and the builder didn't put enough insulation on the kneewall under the house. He categorically told me that *both* digital thermostats were defective and I should replace them with good 'ol manual ones.

Now, what he said may be true, but it's also just what I'd expect him to say - just like I'd expect the builder to blame Honeywell and the HVAC installer and I'd expect Honeywell to blame the HVAC installer and builder. It's a vicious cycle of CYA.

How can I tell what's the problem? I see a lot of pros on this board who seem to like the digital stats. Our old house had Honeywell digital (non-programmable) stats, and we never had a problem staying comfortable or having a high bill.

Any ideas how I sort out what's really wrong?